GENERAL FEATURES OF QUANTUM CREEP IN HIGH-T-C SUPERCONDUCTORS

Measurements of the relaxation rate Q(T) of superconducting currents h ave been performed on a carefully selected set of dirty and clean high -T-c;. superconductors for temperatures T down to 100 mK and magnetic fields up to 7 T. The extrapolated relaxation rates Q(0) for the dirty compounds indicate that the viscosity experienced by a tunneling vort ex segment is grossly underestimated by the standard Bardeen-Stephen t heory. For the clean compounds a universal value Q(0) congruent to 0.0 22 is found at 1 T, implying that the number of superconducting charge carriers involved in the tunneling of a vortex segment is congruent t o 14.